Hello, I've been streaming for quite a while but I'd like to be able to stream in HD without any lag/fps drops.
Now I was wondering what I have to upgrade to be able to do so because I don't know much about pc's in general

Hmm I can stream 1080p on my i7 920 base clock of 2.6 without any lag. But something I saw with your cpu that is anormal to me is the temp.

I5 on full load with stock fan should be around 60 max you should check your thermal paste and make sure the fan is seated tigh on the Cpu.

Streaming doesn't really use that much cpu if you want to stream wow stuff and have a quad core you'll be fine.

Use xsplit with around 1500kkps speed quality to 10 with Faster rendering on a 1080p resolution and it should work fine

I using these setting and ingame I have 70+ fps on 1920x1080p everything on ultra and stream quality is to its maximum and user who watched it said it was perfect lag free.

No, to all of that.

i7 920 (stock) will probably run at around 80-100% when streaming wow in 1080p, nor is 1500 bitrate enough to stream 1080p without horrendous quality, even at 3000 bitrate the stream goes all blurry when turning around etc.

If you were just streaming a web broswer or whatever, that's another thing though.